Noise-induced hearing loss (NIHL) continues to be one of the most common occupational disorders, even in OSHA compliant workplaces. Prevention of occupational hearing loss is a top priority of the National Occupational Research Agenda (NORA). This proposal is to continue the Daily Exposure Monitoring of Noise (DEMON) Study, a study of a unique intervention to prevent NIHL by use of an innovative technology (QuietDose) that records noise exposure levels inside of hearing protection on a continuous basis. In the first phase of the study, intervention subjects and controls have been recruited and regular downloading of noise exposures is occurring. The second phase of the DEMON study will continue to follow this unique cohort in order to determine the effectiveness of the intervention (in both a mandatory and voluntary use setting), better understand the dose response relationship between noise exposure and hearing loss (including the role of impulsive noise) and also compare the effective attenuation of hearing protection over time with fit tests done at a single point in time.